1. Field of the invention
The present invention relates to an electric power steering apparatus and a method of manufacturing the same, and more particularly, to an electric power steering apparatus which controls a current supplied to a motor to adjust a torque of a steering wheel, thereby solving a catching feeling generated when the steering wheel is rotated from opposite ends to a center, and a method of controlling the same.
2. Description of the Prior Art
In general, a power steering apparatus for a vehicle is used to mitigate a steering force of a steering wheel (handle) to secure a stability of steering. A hydraulic power steering (HPS) system using hydraulic pressure has been widely used as the power steering apparatus according to the related art, but in recent years, an environment-friendly electric power steering (EPS) system which assists a steering force of a driver by using a rotating force of a motor unlike an existing method of using hydraulic pressure is being generally installed in a vehicle.
In the electronic power steering (EPS) system, an electronic control unit (ECU) drives a motor according to a travel condition of a vehicle detected by a speed sensor, a steering sensor, a torque sensor, and the like to give a light and comfortable steering feeling during a low speed travel and give both a heavy steering feeling and an excellent directional stability during a high speed travel, and promptly provides a restoring force to the steering wheel according to a rotation angle of the steering wheel to enable a rapid steering operation in an emergency situation, providing a driver with an optimum steering condition.
Meanwhile, in the electric steering apparatus, a motor is installed outside a steering column disposed between the steering wheel and a gear box to rotate a steering shaft such that a rotating force of the steering wheel of a driver may be transferred to a lower side, to assist a steering force of the driver according to a steering operation of the steering wheel.
Meanwhile, the electric power steering apparatus includes a rack end stop function to prevent the steering wheel from experiencing mechanical contacts at opposite ends thereof to generate noise when a driver rotates the steering wheel to a right or left end.
The rack end stop function reduces a current supplied to a motor before the steering wheel mechanically contacts an end to reduce an auxiliary torque when the driver rotates the steering wheel toward the right or left end, thereby preventing the steering wheel from mechanically contacting the end.
By using the rack end stop function, an output required by the motor increases but an auxiliary torque is reduced when the driver rotates the steering wheel from the right or left end toward the center, thereby allowing the driver to feel a catching feeling. Accordingly, there is a need to eliminate a catching feeling that may be felt by the driver.